According to a researcher who has been briefed on the vulnerability, it works by exploiting a four-way handshake that’s used to establish a key for encrypting traffic. During the third step, the key can be resent multiple times. When it’s resent in certain ways, a cryptographic nonce can be reused in a way that completely undermines the encryption.

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It wasn’t possible to confirm the details reported in the CERT advisory or to assess the severity at the time this post was going live. If eavesdropping or hijacking scenarios turn out to be easy to pull off, people should avoid using Wi-Fi whenever possible until a patch or mitigation is in place.